The invention relates generally to measurement tools. In particular, the invention relates to a tool for measuring the surface profile of a valve seat pocket.
A valve is a device that regulates the flow of a material by opening, closing, or partially obstructing a path though the valve. The material flowing through the valve may be a gas, a liquid, a fluidized solid, or slurry. There are a variety of different types of valves, such as gate valves and globe valves.
A valve typically consists of several parts, such as a valve body, a bonnet, a valve member, and a valve seat. The valve body and the bonnet form the casing that contains and directs material through the valve. For example, the valve body may have a bore that extends through the valve body. The valve member interacts with the valve body to control the flow of material passing through the valve. The valve member may be positioned to close or restrict flow through the valve body. For example, a sliding gate may be used as a valve member. The sliding gate may have an opening through the gate so that when the opening is aligned with the bore through the valve body, fluid flow through the bore is enabled. Alternatively, the gate may be positioned so that a solid portion of the gate is aligned with the passage through the valve body, thereby blocking flow through the passage. The valve member is located in a cavity in the valve body that is covered by the bonnet. The bonnet also supports the valve member. During manufacture, the internal parts of the valve are put into the valve body and then the bonnet is attached to hold the valve parts together. The bonnet is removed to provide access to the internal parts of the valve during maintenance.
In a gate valve, the valve seat is the interior surface in the valve body that contacts the gate to form a seal. The gate comes into contact with the seat when the valve is shut. The body and the seat could both come in a single piece of solid material. Alternatively, the seat could be a separate valve part that is attached or fixed to a seat pocket on the inside of the valve body.
When the seat is a separate valve part, the dimensions of the seat and seat pocket must correspond or the seat will not sit properly within the seat pocket of the valve body. As a result, the gate and seat may not properly seal when the valve is closed. In this event, leakage through the valve may occur.
Unfortunately, the dimensions of seat pockets are not easy to measure. Seat pockets typically are cylindrically-shaped regions formed in the passage through the valve body. The roundness of the seat pocket, as well as other surface properties, is difficult to measure or is time-consuming using conventional tools, such as calipers.
Therefore, a more effective technique for establishing the surface properties of a seat pocket of a valve is desired. In particular, a technique is needed to detect the smoothness and roundness of a seat pocket of a bore of a gate valve.